Heat-transmission tube



2 Sheets-Sheet H. W. PAULUS HEAT TRANSMISSION TUBE Filed March 18, 1926 @if y ToEY May 29, i928. l,67,446

H. W. PAULUS HEAT TRANSMISSION TUBE Filed March 18, 1926 2 Sheets-Sheet 2 @www ATTORNEY MVM.

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rr e Y srar HERMAN VW. PAULUS, OF RICHMOND HILL, NEW YORK, ASSIGNOR TO ROYAL BAKING POWDER COMPANY, A CORPORATION OF NEW JERSEY.

HEAT-TRANSMISSION TUBE.

Application led March 18, 1926. Serial No. 95,549.

The invention relates to improvements in heat transmission tubes for chemical apparatus and the like.

Heat transmission tubes are put to a large variety of uses in chemical and allied industries to facilitate chemical reactions and for other purposes. Such tubes have been constructed in many ways, depending upon the character of the uses to which they are put. The heat transmission tubes used in acid evaporators are composite and usually consist of an inner copper tube and an outer lead tube, the copper and lead tubes being bonded together by solder. A. large number of such composite tubes, usually in groups of four, are arranged horizontally in the acid evaporator and are supported y at their ends in opposite side walls or tube sheets of the evaporator. These composite heat transmission tubes have a relatively short life and since Vthey are expensive, many efforts have been made to provide a suitable substitute for them. Up to the present time, however, no satisfactory substitute has been found for the composite copper, solder and lead tubes. Vhen they are Worn out they are. replaced and the expense is charged off to the cost ofoperation.

One reason why these composite tubes are so t uickly damaged and worn out isbecause medhanical considerations require that the outer lead tube be comparatively thin. 1When a comparatively thick lead tube is used, it is found that the difference between the co-elieient of expansion of copper and the co-eficient of expansion of lead causes'a shearing action between the lead and copper` tubes which disrupts the lead tube and cxposes the copper tube to the corrosive action of the acids. Hence the walls of the lead tube must be sufficiently thin to minimize the effects of the shearing action caused by the differences in expansion between the two tubes. The thin lead tubes, however, are mechanically weak and the mechanical injuries to which they are necessarily subjected in the operation of the apparatus detaches portions of them at various points, exposing the corrodible copper to chemicals and thereby necessitating replacement of the unit.

The object of the present invention is to produce a heat transmission tube. for chem1- cal apparatus and the like which will be acid resistant, mechanically strong, sublect to no shearing'action, and relatively unaffected by expansion and contraction. To the accomplishment of this object the invention consists in the improved heat transmission tube hereinafter fully described and particularly pointed out in the` appended clalms.

In the accompanying drawings illustrating the preferred form of the invention and the application of the improved heat transmission tube to` an acid evaporator, Fig. 1 is a longitudinal section through a conventional form of acid evaporator, showin a series ofthe improved heat transmission tubes located therein;'Fig. 2 is an enlarged longitudinal section'through one of the improved heat transmission tubes and through adjacent portions of the tube sheets or side walls of the evaporator, and a side elevation of one of the tubes; Fig. 3 is an end elevation of the parts shown in Fig. 2; Fig. 4 is a section taken along the line 4-4 of Fig. 2; Figs. 5 and 6 are transverse sections through modified forms of tubes; and Fig. 7 is a partial longitudinal section through a third modified form of tube.

The conventional form of acid evaporator shown in Fig. 1 may be taken as typical of the chemical apparatus in which the heat transmission tubes of the present invention are adapted for use. This acid evaporator comprises a vacuum pan 10 of any preferred form provided at its upper part with a vapor or vacuumizing duct l1. The supply of liquid to be evaporated or otherwise treated is drawn into the pan 10 through the inlet 12 in the converging bottom walls 13 of the pan, in the lowest part of which is a valve controlled outlet 14. The improved heat transmission tubes of the present invention, generally indicated in Fig. 1 at 15, are used in the same manner in which the composite tubes of the prior art are used. They are arranged lhorizontally in the evaporator in groups of four (as shown in Fig. 3) and their open outer ends pass through and are supported in the side walls or tube 'sheets 17 and 18 of the evaporator. Steam is admitted through a pipe 19 into a head 20 mounted on one side of the evaporator and into which the inlet ends of the tubes project. The discharge ends of the tubesproject into a similar head 21 mounted on the opposite side of the evaporator land a valve controlled pipe 22 connected with the head 21 conducts away' the exhaust steam.

The improved heat transmission tube of the present invention comprises an outer `member 24 which is a single, preferably homogeneous tube of lead or other non-resilient metal, and an inner member 25 so constructed as to permit the free passage of the heat- -ing or cooling medium throughout the length of the outer member. The preferred arrangement of the outer member or lead tube 24 and inner supporting member 25 is shown in Figs. 2 and 4, in which it is seen that the member 24 is a homogeneous tube throughout its length and that thesupportin member 25 is a. perforated pipe of slightly smaller outside diameter than the inside diameter of th-e tube 24 so as to secure the greatest heat conductivity. The outer lead tube rests on the inner supporting tube (which is preferably of steel), and since there is no physical bond between them the difference of expansion of the two tubes will have no effect u on either. Hence the walls of the lead tu e may be made thick enough to withstand the ordinary mechanical injuries and the pressures it will be subjected to in the operation of the apparatus. rllhis yabsence of a physical bond between the outer leadtube and the inner supporting member minimizes the edect of electroylsis. Instead of the perforated round tube 25 shown in Figs. 2 and 4, ll may use as the inner supporting member the perforated star-shaped tube 26 shown in Fig. 5, or the spider-shaped rod 27 shown in Fig. 6, or the twisted rod 23 shown in Fig. 7.

From a consideration of the four forms of supporting members shown in Figs. 4, 5, 6 and 7, it will be understood that the heat transmission medium has free access to the interior surfaces of the lead tubes 24. Moreover, the inner or supporting members are of such construction and arrangement throughout their length that there is a free passage of the heat transmission medium through them from the intake chamber 20 to the outlet chamber 21. Each'inner, supporting member is rigid enough to support the Weight of the middle section of the lead tube and so prevent sagging. The arrangement of the lead tube and inner perforated supporting tube shown in Figs. 2 and 4 has proven highly satisfactory in use over a long period of time and I prefer to use this arrangement, although the other forms of inner supportingmembers 'alsovgive satisfactory service.

The inlet ends 30 of the improved tubes pass through holes 31 in the side wall or tube sheet 17 and the outlet ends 32 of the tubes through the holes 33 in the side wall ortube sheet 18. The holes 31 and 33 are of such diameter as to permit the ready passage of the tubes 15 therethrough when they are inserted into place and removed therefrom maratea for replacement. A tight joint is made between each end of each tube 15 and the hole in the tube sheet through which it projects by means of a collar 35 of rubber or other acid resisting compound which lits tightly over the reduced outer end 36 ofthe tube. Each collar 35 is cone-shaped on its inner end 37 and fits into the correspondingly countersunk outer end38 of the hole 31 or 33 into which it tits. Each group of four collars 35 are held in position by a plate 39 secured against the outer side of its respective side wall or tube sheet by means of a stud 40 and nut 41. The inner perforated tubes 25 are long enough to project outward- 1y at their ends 42 through the holes 43 formed in the corners of the plates 39. It will be observed from a consideration of Fig. 2 that at the points where the outer ends of the tubes 24 extend through the side walls or tube sheets 17 and 18, the tubes 24 are contracted to fit tightly upon the ends of the inner perforated tubes 25. The construction is such as to permit the passage of the heat transmission medium through the tubes 24 and 25 and to prevent the leakage of liquid through the holes 31 and 33.

Having thus described the invention what l claim as new is l. A heat transmission unit for chemical apparatus andthe like compri-sing, a tube composed of a non-resilient metal arranged to be supported externally at its two extremities only, and a rigid supporting member on which the upper part of the interior of the tube rests, said inner supporting mem- 'ber being substantially as long as the tube and of such construction and arrangement as to permit the passage of a heat transmission medium through the tube.

2. A heat transmission unit for chemical apparatus and the like comprising, a tube composed entirely of llead arranged to be supported externally at its two extremities only, and means for supporting the tube internally consisting of a rigid member sub-l stantially as lon as the tube and located therein and onw ich the upper part of the interior of the tube rests, said inner supporting member being of such construction as to permit the passage of a heat transmission medium through the tube.

3. A heat transmission unit for chemical apparatus and the like comprising, an outer tube composed entirely of lead arranged to be supported externally at its two extremities only, and an inner tube composed of rigid material substantially as long as the outer tube and on which the upper part of `the interior of the outer tube rests, said inner llt) 

